1. Field of the Invention
The present invention relates to a microphone apparatus, and more particularly to an acoustic structure, which is applied to a radio apparatus, a recording apparatus and the like in which a microphone is built in a microphone case or a main housing, for resolving the problem in which clarity of voice information to be absorbed is lost by a phenomenon in which transmitting voice with a strong sound pressure or under strong wind, wind noise or prosodic features of voices based on various kinds of languages and individual differences are generated.
2. Description of the Related Art
Conventionally, in a mobile-use radio apparatus, a microphone is built in a microphone case, which is cable-connected to a main body. In a handy-type transceiver, a microphone is built in a housing.
In accordance with miniaturization and supersensitization of the microphone, there has been recently adopted a system wherein a small sound absorbing hole is formed on a microphone case or a housing panel and the microphone is held on the back thereof and a sound perceptible portion of the microphone is fixed to the sound absorbing hole to be opposed thereto in this manner.
However, in the apparatuses used outdoors such as the radio receiver and a transceiver, the following problems occur.
More specifically, a speaker must put one""s mouth close to the sound absorbing hole and utter a loud voice. Moreover, since a strong current of air occurs along the front surface of the panel under the strong wind, a space, which is formed between the absorbing hole of the panel and the sound perceptible portion, functions as a column of air or a sound box and a so-called xe2x80x9cwind noisexe2x80x9d is inputted into the microphone, and this makes it difficult for a receiver side to hear the transmitting sound.
Furthermore, a linear sound guide channel is formed between the absorbing hole of the panel and the sound perceptible portion. Accordingly, when the speaker puts one""s mouth close to the sound absorbing hole as mentioned above, a strong sound pressure caused by breath directly acts on the sound perceptible portion even in an unvoiced state and a breath sound is voice-outputted, thereby grating on a receiver""s ear.
As measures against these problems, the following systems are adopted:
(1) A system in which a portion close to the sound absorbing hole of the panel surface is louvered and the current of air is scattered to prevent occurrence of resonance;
(2) A system in which a sponge or like is interposed between the sound absorbing hole and the sound perceptible portion to eliminate an element such as a column of air or the sound box in order to prevent the sound pressure caused by breath from being directly applied to the sound perceptible portion; and
(3) The size of the sound absorbing hole is formed as small as possible, and the sound guide channel is bent at the right angle twice to be guided to the sound perceptible portion of the microphone.
However, since various resonant conditions and sound pressure propagation conditions may be established depending on the state of the sound pressure caused by the uttered sound close to the panel surface and the direction of the wind, univocal louver formation as adopted in measures (1) cannot solve the aforementioned problems. In addition, it is almost impossible to form an ideal louver.
Measures (2) are substantially useful for the wind noise, breath sound and the like. However, this reduces sensitivity as a sound absorbing system and particularly attenuates high frequency components of voice frequency considerably, thereby deteriorating the reception quality on the receiver side.
Measures (3) are useful for the breath sound since the reduction in the sound absorbing hole lowers the sound absorbing efficiency. However, there is no effect on the wind noise since the sound guide channel functions as an element of the column of air.
In the radio apparatus used outdoors, conditions such as the state of noise, direction of the wind, wind force, and the like are frequently changed, and a microphone use environment is variously considered. It is naturally desired that high-quality transmission system be always maintained in any condition.
In addition, the voices represent a great variety of prosodic features based on kinds of languages such English, French, and so on and individual differences in pronunciation characteristics. There has been experimentally known a problem in which the transmission system does not match a voice with a specific prosodic feature and particularly consonants, which belong to the high frequency, become unclear. Microphone apparatuses that are adaptable to such individual circumstances are most desirable.
The aforementioned problems and demands are not limited to the radio apparatuses, and the same can be applied to the portable recording apparatuses.
In consideration of the aforementioned problems, it is an object of the present invention to provide a microphone apparatus, which can easily adjust a transmission system from a panel front surface side in response to circumstances, whereby making it possible to input a high quality voice having neither wind noise nor a breath sound generated and to implement the input of clear voice against various kinds of prosodic features of the voice.
According to the first aspect of the present invention, there is provided a microphone apparatus, which guides a wave form to a perceptible portion of a microphone from a sound absorbing hole formed on a panel through a sound guide channel, comprising an adjusting mechanism, the adjusting mechanism having: a sound box interposed between two inner wall surfaces parallel to the panel in the sound guide channel; a movable piece moving in slidably contact with each inner wall surface as ensuring a ventilation channel between the sound absorbing hole and the sound perceptible portion in the interior of the sound box; a screw rod installed in a standing manner in a direction parallel to the panel with respect to the movable piece, the screw rod passed through a hole formed on a frame wall portion of the sound box to be projected outside; a screw hole formed at a central portion into which the screw rod is screwed; a disk having a part of a side peripheral surface exposed to the front surface from a window formed on the panel; and a support portion for restricting and supporting the disk to be prevented from being moved in a direction parallel to the panel.
According to this invention, the part of the disk exposed to the front surface of the panel is rotated by a manual operation with an operator""s finger, whereby making it possible to move the movable piece, which is integral with the screw rod up and down in the sound box based on the pair of the disk restricted by the support portion and the screw rod.
As a result, the sound box functions as a variable sound filter, and the resonant frequency of the sound guide system is changed by the adaptable rotating operation of the disk, whereby making it possible to adjust the variable sound filter to prevent wind noise and the breath sound and the like from being inputted into the microphone.
Additionally, the adjustment of the variable sound filter can structure the optimal sound input system, which is adaptable to even various kinds of prosodic features of the voice.
According to the second aspect of the present invention, there is provided a microphone apparatus, which guides a wave form to a perceptible portion of a microphone from a sound absorbing hole formed on a panel through a sound guide channel, comprising an adjusting mechanism, the adjusting mechanism having: a sound box interposed, as a disk space, between two inner wall surfaces parallel to the panel in the sound guide channel, the sound box having holes, which are guided from the sound absorbing hole and the sound perceptible portion, formed at non-opposite positions with respect to each wall surface, and the sound box including a rim portion and a central plate portion wherein the rim portion has a plane shape formed by partially cutting a disk, a side portion and an outer peripheral surface being in slidably contact with each inner wall surface and inner peripheral surface and the central plate portion is formed at the inner side thereof; a rotation piece serving as an inner gear element with tooth formed on the inner peripheral side surface of the rim portion; a small gear, placed between the central plate portion of the rotation piece and the inner wall surface of the panel side, for meshing with an inner gear of the rim portion; and a round axial rod installed about the small gear in a standing manner to be passed through around hole formed on the panel.
According to this invention, the sound box functions as a variable sound filter similar to the first invention. However, the resonant frequency of the sound guide system is changed when the rotation piece is rotated in the sound box. In other words, the respective holes, which are guided from the sound absorbing hole and the sound perceptible portion, are formed at non-opposite positions, and the shape of the ventilation channel formed between the respective holes is changed by the angle of rotation of the rotation piece. As a result, the resonant frequency of the entirety of the sound guide system is changed, so as to obtain the similar effect.
The adjustment of the rotation piece is carried out by rotating the round axial rod passed through the round hole of the panel. Then, the rotation piece is rotated in the sound box based on the meshing relationship between the small gear, which rotates with the round axial rod, and the inner gear of the rotation piece side.
Additionally, as the rotating operation system of the round axial rod, there can be adopted a system in which a slit is formed on the tip end of the round axial rod and is rotated by a driver and the like and a system in which the round axial rod is projected from the panel surface and a knob is attached thereto and the knob is operated.